The present disclosure generally relates to force and deceleration delimiting devices, and more particularly, to expandable volume filling mechanical structures that generally maintain a compressed volume and rapidly deploy to an expanded volume in response to a triggering event. The expanded volume provides energy absorbing properties to objects impacting the devices.
In the vehicular arts, there are generally two types of dedicated crash energy management structures utilized for minimizing the effect of an impact event: those that are passive, and those that are active. The active used in this context refers to selective expansion or movement of one component relative to another component to minimize the effect of an impact event.
Typically, passive energy absorbing structures have a static configuration in which their volume is fixed. The passive energy absorbing structures can dissipate energy and modify the levels and timing of a force/deceleration pulse by being impacted (e.g., crushing or stroking of a piston in a cylinder) so as to absorb the kinetic energy associated with such an event. Since these passive crash energy management structures occupy a maximum volume in the uncrushed/unstroked initial state, these types of structures inherently occupy significant vehicular space that must be dedicated for crash energy management and/or occupant protection—the contraction space being otherwise unavailable for other use. Expressed another way, passive crash energy management and occupant protection structures use vehicular space equal to their initial volume, which consequently must be dedicated exclusively to impact energy management and/or occupant protection throughout the life of the vehicle. Because of this, some areas of a vehicle interior and/or exterior may be constrained in terms of their design/appearance because of the volume requirements of passive crash energy management and occupant protection devices.
An example of a passive energy absorbing structure that has been used in vehicles is an expanded honeycomb celled material, which is disposed in the expanded form within the vehicle environment. FIG. 1 illustrates a honeycomb celled material and its process flow for fabricating the honeycomb-celled material. A roll 10 of sheet material having a preselected width W is cut to provide a number of substrate sheets 12, each sheet having a number of closely spaced adhesive strips 14. The sheets 12 are stacked and the adhesive cured to thereby form a block 16 having a thickness T. The block 16 is then cut into appropriate lengths L to thereby provide so-called bricks 18. The bricks 18 are then expanded by physical separation of the upper and lower faces 20, 22, where adhesive strips serve as nodes to form the honeycomb cells. A fully expanded brick is composed of a honeycomb celled material 24 having clearly apparent hexagonally shaped cells 26. The ratio of the original thickness T to the expanded thickness T′ is between about 1 to 20 to about 1 to 60. The honeycomb celled material is then used in fully expanded form within the vehicle environment to provide impact energy management and/or occupant protection (through force and deceleration limiting) substantially parallel to the cellular axis. As noted, because the honeycomb material is used in the fully expanded form, significant vehicular space is used to accommodate the expanded form, which space is permanently occupied by this dedicated energy management/occupant protection structure.
Active energy absorbing/occupant protection structures generally have a predetermined size that expands or moves in response to a triggering event so as to increase their contribution to crash energy management/occupant protection. One type of dedicated active energy absorbing/occupant protection structure is a stroking device, basically in the form of a piston and cylinder arrangement. Stroking devices can be designed, if desired, to have low forces in extension and significantly higher forces in compression (such as an extendable/retractable bumper system) which is, for example, installed at either the fore or aft end of the vehicle and oriented in the anticipated direction of crash induced crush. The rods of such devices would be extended to span the previously empty spaces in response to a triggering event, e.g., upon the detection of an imminent impact event or an occurring impact event (if located ahead of the crush front). This extension could be triggered alternatively by signals from a pre-crash warning system or from crash sensors or be a mechanical response to the crash itself. An example would be a forward extension of the rod due to its inertia under a high G crash pulse. Downsides of such an approach include high mass and limited expansion ratio.
Another example of an active energy absorbing/force and/or deceleration limiting structure is an impact protection curtain, e.g., a roll down inflatable shade that may cover a window opening in response to a triggering event. The roll down curtain, while being flexible in bending when out of plane, is quite stiff in-plane. Other devices, such as inflatable curtains, while inflated, act to help cushion the occupant upon impact.
Therefore, missing in the art are expandable energy absorbing/force and/or deceleration limiting devices for impact attenuation.